1. Field of the Invention
The present invention relates to a liquid supply apparatus and method, and to an inkjet recording apparatus, and more particularly relates to an apparatus and method for supplying liquid for ejection to a liquid ejection head, and an inkjet recording apparatus using the liquid supply apparatus.
2. Description of the Related Art
An inkjet recording apparatus forms images by supplying ink to a print head (also called a recording head) from an ink tank, through ink supply paths, ejecting ink from nozzles of the print head by selectively driving ejection driving elements (pressure generating elements such as piezoelectric elements, heating elements or the like) corresponding to the respective nozzles, and depositing the ink droplets thus created onto a recording medium. In an inkjet recording apparatus of this kind, it is necessary to achieve stable ink ejection, and many different technologies have been proposed for this purpose.
Japanese Patent Application Publication No. 8-156280 suggests the provision of a temperature adjustment device for adjusting the temperature partially, only in prescribed sections, such as a filter member provided in an ink supply channel, in order to achieve a constant ink ejection volume and ejection frequency. By means of this composition, the negative pressure inside the ink tank is stabilized in accordance with the ink characteristics, the viscous resistance of the ink is reduced inside the ink supply channel (and especially, the filter section) during high-duty printing, and increased pressure loss in the filter section due to increased ink viscosity can be prevented. Therefore, it is possible to stabilize the ejection characteristics, even in the case of high-duty printing.
Japanese Patent Application Publication No. 2003-127417 suggests that a heating device capable of heating the vicinity of a filter interposed in an ink channel is provided, thereby heating the ink passing through the filter section and thus lowering the viscosity of the ink. Consequently, the flow resistance is reduced, stable ejection is achieved, and the replenishment (refilling) speed of the ink is increased.
However, although the method disclosed in Japanese Patent Application Publication No. 8-156280 has the beneficial effect of reducing the viscous resistance on the downstream side of a prescribed section (for example, the filter section) of the ink supply system, it does not take account of the changes in viscous resistance on the upstream side. Furthermore, in an ink supply system which uses ink of high viscosity, such as that described in Japanese Patent Application Publication No. 2003-127417, the pressure loss inside the flow channel is dependent on the ink viscosity changing with the operating temperature conditions, and is also dependent on the ink supply flow speed (ink flow rate), and this can lead to variation in the ejection characteristics of the ejection device. However, the method disclosed in Japanese Patent Application Publication No. 2003-127417 has no effect in correcting the pressure for pressure loss variations caused by change in the viscosity drag due to change in the ink flow rate. Furthermore, in Japanese Patent Application Publication No. 2003-127417, the heating system for the whole ink supply system is complicated and large in size, and the temperature control is also complicated.